Question

Why do veins appear blusih green in colour

Answer 1

Hello,
Blood is bright red when oxygenated and very dark red when deoxygenated.

Due to deoxyhaemoglobin.(this means blood is always red)

Now, the veins appear blue because penetration power of blue light is maximum (due to less wavelength than red) and that of red light is minimum.

This is the reason that we see the the veins blue rather than red.

Hope that helps you.
Keep learning.